Listening and ringing key for telephone switchboards



Sept. 9, 1947, BQSH Q 2,427,187

LISTENING AND RINGING KEY FOR TELEPHONE SWITCHBOARDS Filed May 10, 1945 Patented Sept. 9, 1947 LISTENING AND RINGING KEY FOR TELE- PHONE SWITCHBOARDS James E. Bosh, Berwyn,

Switchboard and Sup Ill., a corporation of Illi 111., assignor to Kellogg ly Company, Chicago, nois Application May 10, 1945, Serial No. 592,932

7 Claims.

This invention relates to switching keys, and is particularly concerned with keys of the type used as ringing and listening keys in telephone switchboards.

As disclosed, for example, in the U. S. Patent No. 1,508,798, such a key comprises a pivotally mounted cam carrying actuating rollers of insulating material for selectively operating sets of contact springs arranged on either side thereof. The operation is effected by means of a lever or handle which may be tilted to one side or the other for the purpose of rotating the cam to dis place the rollers into operative position with respect to the corresponding contact springs.

The prior patent recognizes as a source of trouble the rebound action of the key lever with its cam and rollers incident to its return from either of its operating positions to its normal position. Such rebound action causes chattering, i. e., vibration or oscillation of the operating parts including the rollers, and such chattering in turn may produce momentary actuation of the contacts and consequent, disturbance of the circuits controlled by such contacts. The remedy proposed in the prior patent resides in the provision of spring means for cushioning the lever-operated cam incident to its displacement to one side, and a second spring means for cushioning the cam incident to its displacement to the opposite side.

The present invention improves upon the prior structure by the provision of a pair of snubber springs, each of which is arranged for elastic coaction with the key cam in either direction of operation. The new snubber springs jointly control the operating parts, that is, the key lever, the cam and the actuating rollers, throughout the displacement of these parts from normal to either actuated position and throughout their return to normal from either position.

The new arrangement provides a positive control for the operating parts and furnishes the desired cushioning and dampening, with greater assurance of avoiding the rebound action, and thus prevents chattering of the contact springs. The new arrangement also aligns the key cam in its normal position so that the handle is positioned perpendicular to the front face of the key escutcheon. In addition, the new arrangement provides a detent effect to assure a positive action of the cam to its fully operated position in either direction of operation.

These and other objects and features of the invention will appear from the detailed description which is rendered below'with reference to the accompanying drawings, showing a preferred embodiment. In these drawings,

Fig. 1 represents a side view of a switching key made in accordance with the invention;

Fig. 2 is a right end view of Fig. 1;

Fig. 3 shows a side or edge view of the new snubber spring; and

Figs. 4 and 5 illustrate the new key in its two operating positions.

The drawings are more or less schematic and are only intended for descriptive and illustrative purposes. Well known details and elements will be described merely to the extent required for conveying an understanding of what is believed to be new. The various parts are indicated by identical reference numerals throughout the drawings.

The new key comprises a generally T-shaped frame having a rib or wall H and a base 12. A washer I3 is provided for deadening noise. The base of the frame and the washer are fastened to the escutcheon plate M by means of screws, as shown, with the frame rib ll extending perpendicularly from the escutcheon plate in back thereof. Suitably mounted on the rib ll of the frame are sets of contact springs generally indicated at [5 and [6. There are two sets of contact springs IE on the left of the frame rib H and two similar sets of contact springs IS on the right of the frame rib. An operating cam IT is pivotally mounted in the frame by means of a pin it. The frame base l2 and the rib are for this purpose slotted, as indicated in Fig. 2 by numeral 3%. The cam I1 extends to the outside and partially projects from the front face of the escutcheon plate 14. A handle or lever i9, which is made of insulating material, is attached to the projecting portion of the cam, and the insulating rollers 20 are rotatably mounted on the cam extension 2| in back of the escutcheon plate. There are two such rollers, one for operating the sets of contacts l5 and [6 on the side of the key shown in Figs. 1, 4 and 5 and the other for operating similar sets of contacts on the other side.

In normal position, shown in Fig. 1, the rollers 26 are disposed between and out of engagement with the actuating springs 2'2 and 23 of the corresponding sets of contacts. In the operated position shown in Fig. 4 the rollers 20 are in engagement with the operating springs 23 of the sets of contacts I6 on the right of the frame rib ii and have flexed these springs, as shown, so as to establish the illustrated contact conditions, with the inner contacts open and the outer contacts closed; and in the other operated position, shown in Fig. 5, the rollers are in engagement with the springs 22 of the sets of contacts 15 on the left of the frame rib l I and have flexed these springs to establish corresponding contact conditions.

The cam is provided with projections or ears 24, generally radially extending therefrom below the pivot point [8 for coaction with the new snubber springs 2521. In normal position of the key, as shown in Fig. 1, the ear 24 is disposed in a groove formed in the upper crimped-portion' of the snubber spring 26, and the ear25 is-similarly disposed in the groove formedin-the upper crimped portion of the snubberv spring- 21.

The two snubber springs are shaped alike.- Spring 26 is assembled together with the set of contact springs l5 disposed at the left" of the frame rib II at the forward edge thereof, as seen in Figs. 1, 4. and 5; and the snubber spring 21 is turned around 180 with respect to spring 25 and is assembled together with the set of contact springs l6 disposed atthe right, of the frame rib H at the rearward end'thereof, as: seen in Figs. 1, 4. and 5, or right as seen in Fig. 2.

As shown in Figs. 2 and 3, thesnubberv spring has a lower mounting section 28, a central section 29 which is offset from the median center line of the mounting section 28 and an upwardly extending section 32 which is disposed in alignment with the corresponding edge of the cam l1 and is crimped at the free end to provide a groove 3|. for engagement with the corresponding ear or projection of the cam, aspreviously described. The free end of the snubber spring above the groove 3| is offset outwardly from the plane of the section 32, as seen in Fig. 3, for the purpose of facilitating the assembly of the springs on the key and their coaction with thecam; and the lower sections 29', 28 are offset inwardly from the plane of the section 32'for the purpose of pro-- viding inward pressure of the, snubber springs with respect to the cam when the springs are mounted as shown. The. snubber spring. isproduced from a suitablemetal sheet in simple punching and forming. operations. The specific angular displacement of the sections 28, 28 and of the free upper, end of. the snubber spring with respect. to the plane of section 32, as indicated in- Fig. 3, is'used in a certain-practicalembodiment, and is shown in the drawingmerely to give an example. As noted. above, the displacement is provided for. the purpose of biasing the snubber springs on eachside of the key inwardly in the direction of the cam, so that the snubber springs engage the'cam with, a certain pressure. The pressure that may be required in any given case may call for different angular displacement of the corresponding springv sections, dependingonfactors suchasthe size of the parts, the spring material, the thickness of the spring, and others.

The alignment of the key cam in its normal position, so that the handle. l9.- is disposed perpendicular to the front face of the key escutcheon I4, is apparent from Fig. l. The; ears or, projections 24, 25 of the cam are disposed and elastically locked within the grooves-formed. in the crimped upper ends of the snubber. springs, 26 and 21. The springs exert an inward pressure; that is, they engage the'ears or projections 24, 25 of the cam with a pressure applied-below the pivot point 18 and of substantiallythe samemagnitude on each side of the cam. The result is that the cam is aligned as statedand as shown in Fig. 1, the snubber springs preventing inadvertent angular displacement of the cam from this normal position. The action is positive, the ears or projections 24, 25 operating in the nature of stops which are held elastically in normal position by engagement with the positively disposed llocking, grooves in.the springs.

The detenti function of the new: arrangement, which assures positive action of the cam to its fully operated position in either direction of operation, may be explained with reference to Figs. 4* and 5.

Displacement of the key handle I!) from its normal position shown in Fig. 1 to the left, to the operated position as seen in Fig. 4, rotates the. cam I'lin counter-clockwise direction, thus moving theear or projection 24 downwardly out of the groove inthe snubber spring 26 and moving theyear or projection 25 upwardly out of the groove in the snubber spring 21. The resulting angular displacement. shifts the lever arms formedby these. earsv or projections incoaction with thesnubbersprings, thelever arm formed by the ear orprojection 24' allowing the full force.of.spring. 26 to, become effective, overbalancingthe pressure of spring 21, thus tending to continue the counter-clockwise rotation of, the cam. The ear'or projection 25 rides up on the upperv end of 'thesnubber spring 21. incushioning and dampening engagement with the snubber spring. The counter-clockwise rotation.- of. the cam continues untillthecam hasreachedits fully operated position withthe. contact. sets 16 properly actuated.

The. operation of the. key from its normal position-illustrated inFig. 1, intothe position shown in.Fig. 5; is. similar except, oi?v course, that the lever. action described with reference to the cam ear. 24 applies, to the. cam. ear. or projection 25.

which is pressed inwardly by the-snubber spring 21 witha force greater thanthepressure exertedby the, springifi. onthe. cam ear or projection 24. Theresult is thatthe angular displacementor. rotation of thercamv H in clockwise directioncontinues until the cam is in fully operated-positionwiththe contact sets l5 actuated as shown.

The cushioningand dampening function of the snubber springs 2B-and 2.1. to prevent rebound of the cam and its associated parts becomes operative when thekey. isrestored from either operated. positionshown in Figs. 4 and 5 to the normal positionillustrateddn Fig. 1.

Operation. of. the key handle to the right, as seen in Fig. 4, to restore it to. normal, rotates the cam. in clockwise direction. Such rotation is opposedby. the pressure of thesnubber spring 26. exertedon the ear or projection 24- for the same reason that: the. pressure of this spring assisted thev counter-clockwise operative rotation of the cam, as. previously described. The clockwise restoring motion of the, cam is thus dampened-and cushioned. The dampening and cushioning. action. persists until the-earv 24 has reachedthe lower. crest ofthe crimp inspring 26; readyto move into its-stop groove. The, ear or: projectionv 25 reaches at the same time the upper crest of the stop groove in spring 21. During the further clockwise restoring motion of the-cam the upper andouter surface of the ear or projection 25. becomes aligned with the corresponding surface inIthe. stop groove of snubber springZ'Lsubstantially inparallel therewith and ready to slide-intothis groove, while the ear 24 is, positioned substantiallyperpendicular to. the

lower surface of the stop groove in spring 26, thus providing a brake action which opposes the entrance of the ear 24 into its stop groove. The dampening and cushioning action thus persists for the remainder of the clockwise rotation of the cam to normal, until the ears or projections 24, 25 have reached their proper positions in their stop grooves, when the rotation of the cam to normal position is effectively stopped and arrested. Vibration or oscillation of the cam, and

therewith the rollers 20 and consequently momentary operation or chattering of the contacts is thus prevented.

The cushioning and dampening effect is likewise operative in a similar manner when the key handle is actuated to normal from the position shown in Fig. 5, except that the coaction of the snubber springs with the cam ears follows in reverse order. In other words, what has been said with respect to snubber spring 26 and its coaction with the cam ear 24 applies the latter case to snubber spring 21 and cam ear 25; and the action described with respect to spring 21 and cam 25 applies to spring 26 and cam 24.

Changes may be made within the spirit and scope of the appended claims which define what is believed to be new and desired to have protected by Letters Patent of the United States.

I claim:

1. In an operator's key having a frame mounted on an escutcheon plate and carrying sets of contact springs and a pivotally mounted rotatable cam provided with an operating handle projecting from the escutcheon plate and hav ing means on said cam for actuating said contact springs, a device for controlling the operation of said cam comprising separate spring means for coaction with said cam on either side thereof, each of said spring means being constructed and arranged for elastic engagement with said cam throughout the angular displacement thereof from normal position to operated position and back to normal position in either direction of operation for the three-fold purpose, first. of aligning the cam in its normal position. so that the handle is perpendicular to the front face of the escutcheon plate, second, of providing a detent action to assure positive actuation of the cam to its fully operated position, and third, to cause the cam to return. to its normal position and come to rest without rebound so as to prevent inadvertent actuation of said contacts.

2. In an operator's key having a frame carrying sets of contact springs and a. pivotally mounted rotatable cam provided with an operating handle and having means for actuating said contact springs, a device for controlling the operation of said cam comprising separate spring means for coaction with said cam on either side thereof, each of said spring means being constructed and arranged for elastic engagement with said cam throughout the angular displacement thereof from normal position to operated position and back to normal position in either direction of operation thereof.

3. The structure and combination defined in claim 2, wherein said cam is provided with a projection extending therefrom on either side thereof, and wherein each of said separate spring means is provided with a groove for receiving the associated cam projection in normal stop position of the cam.

4. In an operators key of the class described having a generally T-shaped member forming a rib carrying a set of contact springs mounted on either side thereof which extend substantially in parallel with said rib and having a cam which is pivotally mounted for angular displacement to either side for the purpose of actuating the contact springs mounted on either side of said rib, the improvement which consists in the provision of separate spring means disposed on each of said sets of contact springs outside thereof and extending substantially in parallel with said contact springs on either side of said rib for elastic engagement with said cam to cushion and to dampen the angular displacement thereof.

5. A device of the class described, including an escutcheon plate, a generally T-shaped mounting frame secured thereto and forming a rib carrying a set of contact springs secured to either side thereof, a cam member pivotally supported in the base of said T-shaped mounting frame and provided with means for operating said sets of contact springs, and auxiliary spring means disposed on each contact set outside thereof, said auxiliary spring means forming extensions for elastic engagement with said cam member peripherally on opposite sides thereof.

6. In a, key switch having a mounting member carrying a set of contact springs which extend generally in parallel therewith and provided with a pivotally mounted cam carrying means for actuating said contact springs responsive to angular displacement of said cam, a device for controlling the operation of said cam, said device comprising a pair of leaf springs disposed generally in parallel with said contact springs and secured therewith on said mounting member, the free ends of said leaf springs extending beyond said contact springs into elastic engagement with said cam peripherally on opposite sides thereof along a line disposed below the pivot point of the cam to exert substantially equal generally radially inwardly directed pressure on said cam from opposite sides thereof throughout its angular displacement in either direction of operation.

'7. The structure and combination defined in claim 6, wherein the free end of each of said leaf springs is crimped to form a groove for locking coaction with a corresponding ear projecting from the cam for the purpose of positively holding said cam in its normal position.

JAMES ,E. BOSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,508,798 Klay Sept. 16, 1924 1,109,947 'Iromp Sept. 8, 1914 

